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FromMedscape Medical News

Breast Milk Drives Growth of Gut Flora, Infant Immune System

Jenni Laidman

May 1, 2012—

Researchers at Texas A&M University caught some of the conversation between gutmicrobes and infant genes that appear to help the breast-fed infant make a safe transition from lifein the womb to life outside, astudy published

April 29 in the open-access journal Genome Biologyreports.

The study, which confirms earlier findings that show breast-feeding gooses the developing immunesystem, elucidated the chatter between genes in the developing infant and the gut bacteria byanalyzing the relationship between bacterial communities found in the guts of 6 breast-fed 3-month-olds and 6 formula-fed 3-month-olds. The researchers compared the gut microbiome information togene expression levels in the infant gut and identified genes involved in immunity and defense withaltered expression levels in relation to the gut bacteria in breast-fed infants.

Scott Schwartz, PhD, an assistant research scientist in the Bioinformatics at Texas A&M University,College Station, and colleagues analyzed fecal samples to determine what kinds of bacteria live in theinfant gut and what the shed infant epithelial cells were doing about it. They found breast-fed babieshad more diverse gut biota, but their immune systems were primed for it.

"While we found that the microbiome of breastfed infants is significantly enriched in genes associatedwith 'virulence,' including resistance to antibiotics and toxic compounds. We also found a correlationbetween bacterial pathogenicity and the expression of host genes associated with immune anddefense mechanisms," corresponding author Robert Chapkin, PhD, professor, Program in IntegrativeNutrition and Complex Disease, Texas A&M University, said in a news release.

"Our findings suggest that human milk promotes the beneficial crosstalk between the immune systemand microbe population in the gut, and maintains intestinal stability," he said in the release.

The researchers found that gut bacteria of 5 of the 6 formula-fed infants were homogenous inphylum-level distributions, with roughly equal proportions of Firmicutes and Actinobacteria—

In contrast, the microbiomes of the breast-fed infants were heterogeneous. Actinobacteria dominatedgut populations in 3 infants. Proteobacteria dominated in another, Bacteroidetes another, and 1infant's gut microbiome was balanced across phyla.

The researchers further isolated infant messenger RNA from feces and looked at expression levels inrelation to the gut ecosystem and found strong relationships between virulence characteristics for gutbacteria and immunity and defense genes.

The authors write that this work provides a "rigorous analyticalframework" to look at host-microberesponses in diet-environment interactions during early infancy.

The study was funded by the National Institutes of Health, the Hatch Project Division of NutritionalSciences Vision, and the United States Department ofAgriculture–

National Institute of Food andAgriculture (USDA–NIFA) Grant Designing Foods for Health. One author is supported by the Collegeof Arts and Science at Miami University. The authors have disclosed no relevant financialrelationships.